Goodbye Twitter. It's been an amazing ride, and I will cherish the memories.

Dick Costolo, Twitter’s CEO, replied: “Thank you for being an incredible executive & partner. Twitter could not have succeeded without you.”

Twitter did not give a reason for Rowghani’s exit. The former Pixar finance chief was one of Costolo’s closest lieutenants and a key player at Twitter, having joined as finance director in 2010. Inside the company he was referred to as “co-CEO” and in April the Wall Street Journal called him Twitter’s “Mr Fix-It”. Twitter said he would continue to act as an adviser to Costolo.

The exit of such a high-profile executive fuelled speculation that Twitter is continuing to struggle with questions about its growth strategy that have dogged the company since it went public last November.

In April Twitter issued its second set of quarterly results as a public company and announced a massive rise in revenues. For the first three months of the year Twitter brought in $250m (£150m), an increase of 119% year on year. But its share price suffered a sharp fall as investors worried about its slowing growth rate.

Twitter sold its shares at $26 apiece last November. They soared on the first day of trading, closing at $44.90, and reached $73 in December but have been on the slide ever since as analysts have highlighted the company’s seeming inability to pick up growth in the US, where it makes 75% of its ad revenue. After the news of Rowghani’s exit they stood at $36.75.

A recent report from eMarketer estimated Twitter would grow nearly 25% in 2014, but mostly in Asia-Pacific countries. The report predicted US growth would fall to a single-digit percentage by 2015.

Rowghani’s departure is the latest in a series of high-profile exits. Twitter’s product chief, Michael Sippey, resigned in January and in May Christopher Fry, the senior vice-president of engineering, left.

News of Rowghani’s resignation surfaced on the tech news site Recode.net, which said he had also caused tension with his decision to sell 300,000 shares in May for $9.9m as Twitter’s share price continued to come under pressure.